Safety closure means for pressurized furnaces



July 23, 1964 H. PHILLIPS ETAL. 3,142,272

SAFETY CLOSURE MEANS FOR PRESSURIZED FURNACES Filed July 2o, 1960 2sheets-sheet 1 A ltorney SAFETY cLosuRE MEANS FOR PRESSURIZED FURNACESFiled July zo, 1960 Jully 28, 1964 H. PHILLIPS ETAL 2 Sheets-Sheet 2N/// U///U//// 'IUEIII A D@ Attorney fluid is either non-existent orinsufficient. of arrangements have been provided to overcome thek UnitedStates Patent O n 3,142,272 SAFETY CLOSURE MEANS EUR PRESSURIZEDFURNACES l j y Henry Phillips, Metuchen, and Bernard E. Paris, Brooklyn,NX., assignors to Foster Wheeler Corporation, New York, N.Y., acorporation of' New York Filed .Iuly 2t), 1960, Ser. No. 44,059 9Claims. (Cl. 11o- 179) The present invention relates to closure meansforp'r'essurized furnaces, and more particularly to safety` arrangementsfor indicating safe and'unsafe conditions of operation of the closuremeans, and/ or preventing operation of the closure means when unsafeconditions exist.

Pressurized furnaces generally include passages or openings in the wallsthereof in order to enable an operator to gain access to the interior ofthe furnace for cleaning and other purposes. ered by a door or cover andsince the cover is opened during operation of the furnace, means areprovided for protecting an operator from the outward rush of the hotproducts of combustion through the passage. Present furnaceinstallations employ a jet-like curtain of fluid or air which originatesnear the cover and-is di-V rected into the passage towards the interiorof the furnace to provide a iluid barrier to combustion gases tending toescape through suchpassages. This fluid barrier principle has beeneffective on the whole, but other factors have entered into the abovewhich present a dangerous condition at times. On occasion, the operatorhas neglected to initiate the flow of fluid causing the barrier and, asa result, the operator suffers injury when the cover is removed toobtain access to the passage.

At other times, the supply of fluid is disrupted through.

mechanical failure, or the ports through which the fluid llows becomesclogged or plugged so that the supply of A number foregoing conditionsand have taken the form of mechanical interlocks to prevent operation ofthe cover unless the iluid supply valve has beenV turned on, or,

means for sensing the pressure of flow of iluid passing.

to the ports have been employed which prevent operation of the coverwhen safe conditions arel not detected.

These arrangements have sulliced more' or less for the purpose, but theyhave not proved completely satisfactory in some instances as forexample,A when the `flow of iluid through the ports, or the pressurewithin the manifold, is of the designed Valuebut the amount or pressureof such iiuid is not sutiicient to prevent ilow of combustion gases inthe event of an increase ofthe furnace pressure above the normaloperating value.

It is an object of the present invention to provide a novel safetyarrangement for closure means'of pressurized furnaces which operateseffectively over a wide range of conditions of operation of the furnaceto indicate thel presence of safe conditions for operating the cover toaccess passages and/or to prevent operation of the cover when unsafeconditions exist.

The present invention therefore, contemplates a novel.

Safety arrangement for closure means which comprises in one formthereof, the combination of a safety device with a cover for anaccesspassage in the wall of a pressurized furnace wherein a curtain offluid is injected into said passage. The safety device indicates thepresence or absence of fluid in the access passage suflicient to preventow of combustion gases. therethrough when the cover is opened. TheIsafety device comprises pressure detecting means which is exposed to thepressure conditions within the access passage and such pressureconditions result from the flow of iluid 3,l42,272 Patented July 28,1964

by the pressure detecting means to outsidethe furnace where it serves toindicate to an operator either safe or unsafe conditions, or, it may beemployed in another form of the invention to control the operation of`mechanism which restrains operation of the cover under certainconditions.

The above and other objects and advantages of the present invention willappear more fully hereinafter from a consideration of the detaileddescription which follows taken together with the accompanying drawingswherein one embodiment of the invention is illustrated.

In the drawing wherein like reference characters refer to like vpartsthroughout the several views,

FIG. 1 is a front elevational view of the closure means with which thepresent invention may be employed;

FIG. 2 is a sectional View taken along KVthe line 2--2 of FIG. l andshows'in particular; the location of the pressure detecting member inthe access passage;

FIG. 3'is a sectional view taken alongV the line 3 3.

of FIG. l; Y I FIG. 4 is an elevational view'of the closure meanssimilar to FIG. 1 and particularly shows van indicatorfor use with thepressure detecting member; n v

FIG. 5 is a front elevational view' of the cover means of FIG. l whichincorporates a modified form ofr theV present'invention'and illustratesthe use of the pressure detectingV member with mechanism for restrainingoperation ofthe cover; and I FIG. 6 is a sectional view of FIG. 5.

Referring now to the drawing and more particularly to FIG. l, a coverassembly generally designated by the numeraly 12A comprises a coverframe 14fwhich is taken along the line 6 6 adapted for mounting on avertical outer casingv 15 (partly 16; the sleeve and opening constitute'an access open-4 ing'29j lThe inner surface of 'wall 16 is lined with asheet 30Vand arranged in front' of the latter are fluid: conductingtubes 31. A plurality of holes or ports 32 are drilled in plate 24andare arranged in a circular row, preferably at equal circumferentialdistances. YHoles 32 are provided for injecting a gaseous'medium underpressure, as for example air, into access opening 29 in a direction awayfrom cover frame 14'.' The high pres-v sure air is supplied to manifoldchamber 26 via a con` nectingA chamber 34 (FIG. 3) which communicateswithv chamber 26 through an opening 36in annular member 22.

An elbow coupling member 37 isV mounted in frame V14 and communicatesconnecting chamber 34 with a source of high pressure air (not shown)through a conduit 38` and a control valve 39 connected thereto. The airinjected into access opening 29 through ports 32 provides a fluidbarrier to the ow of combustion gases toward the cover frame 14. A

One end of the annular member 20 extends into an opening 40 formed inframe 14. A sealing ring 41 is disposed' in a recessed portion of frame14, which encompasses the opening 40, and the ring is adapted to beengaged by a cover 42 for sealing access opening 29 from the outside ofthe furnace. A transparent member or window 43 is provided in cover 42and is mounted in a resilient insert 44 in a recess formed in cover 42.Insert 44 is engaged by a retainer member 47 which is secured to cover42 by a plurality of threaded members 48. Diametrically opposed lugs 49are provided on and adjacent the outer edge of cover 42 and each lug hasan opening to accommodate a stud 50. The studs 50 extend throughopenings formed in a lifting ring 51 and opposite ends of the studs areprovided with limiting pins 53 to secure the cover 42 to ring 51. A pairof hinge members or ears 55 are secured at corresponding ends to liftingring 51 and the other end of the hinge members are provided withopenings to receive a hinge pin 56 which is journalled in a hinge block58 secured to frame 14.

A latch bar 60 is secured, as by welding, to lifting ring 51 and isprovided adjacent the ring with an upstanding hand-gripping handle 61.Latch bar 60 has a depression 62 (FIG. 2) which is engaged by one end ofa threaded clamping member 63, and threaded portion of said membercooperating with the threaded portion of a latch yoke 64. Latch yoke 64is substantially U-shaped and is adapted for pivotal movement on a pin65 which extends through both arms of the yoke adjacent the lowerportions thereof. The opposite ends of the pin 65 are mounted forrotation in bearing blocks 66 secured to frame 14.

Considering the structure thus far described, when air is injectedthrough ports 32 and it is desired to displace cover 42 to an openposition, as shown in broken lines in FIG. 2, a finger-gripping portion67 of clamping member 63 is rotated in the proper direction to elevatethe lower end of said member out of recess 62 and above the uppersurface of latch bar 60, as seen in FIG. 2. The operator then pivotallydisplaces yoke 64 to the broken line position shown in FIG. 2 andthereafter handle 61 is grasped to swing cover 42 away from cover frame14.

As indicated earlier, the closure means along with the fluid-jetstructure of the type described, has operated successfully withmechanical interlocks between the cover and fluid control valve, andwith pressure and ow responsive operable means. However, there are timeswhen for example, the pressure of the combustion gases in the furnaceand in the access passage 29 exceeds a determined design operating valueso that if cover 42 were opened at such time, the pressure of theinjected fluid would not suiiice to prevent flow of the combustion gasesthrough the passage to the furnace exterior. The present invention hasfor an object, among others, to provide an indication to an operator ofan unsafe condition existing in the passage and/ or prevent the operatorfrom moving cover 42 to an open position.

It is known that when jets of air are directed into access passage 29 inthe manner shown in the drawings (FIG. 2), that a partial vacuum existsin the access passage and such vacuum is greatest in the spaceencompassed by member 20 and is at a minimum going toward the apex ofthe cone of the injected air. Beyond the last-mentioned point and goingfurther in the passage towards the furnace interior, the pressurecommences to become positive and increases in value. The Value of thepressure in the access passage is a function of the pressure and flow ofthe injected air and of the pressure of the combustion gases in saidpassage, whereby the resulting pressure may be referred to as theresultant pressure. Thus, if a graphical representation of the pressureconditions existing in access passage 29 could be shown, a plurality ofpressure gradient lines A to G, inclusive, exist as illustrated in FIG.2. In practice, the accurate measurement and exact contours of thepressure areas in the passage are extremely diiiicult to obtain and,therefore, most of the values as disclosed hereinafter for the pressureshould be considered as approximate rather than as exact.

In an actual installation of the closure means and jetair structuredescribed above, the furnace pressure or that of the combustion gaseswas maintained at approximately 20 inches of Water above atmosphericpressure, while the injected air pressure was 60 p.s.i.g. with a flow of235 s.c.f.m. At such conditions of operation the pressure gradient linesE and G actually were determined and measured and were found to have thevalues of 0 inch of water and +3 inches of water respectively, aboveatmospheric pressure. It was found that if the furnace pressure wasincreased above the value stated above, the area of vacuum behind the 0pressure line E would be compressed in the direction of cover 42, or ashifting of the line E in that direction would occur. Consequently, ifin actual operation the furnace pressure would rise sufficiently tobring about the shifting of line E toward adjacent cover 42 combustiongases would rush out of the access passage to the furnace exterior whenthe cover was opened. On the other hand, there is a shifting of line Ein a direction away from the cover 42 when the furnace pressure isreduced so that no danger exists for the operator when cover 42 isopened.

The foregoing description of the pressure conditions in access passage29 is important in understanding the principle upon which the presentinvention operates and is utilized by the present invention toaccomplish its useful function. As shown in FIG. 2, pressure detectingand transmitting means as for example hollow tubular member 70, isprovided and has one end projecting through sleeve 27 so as to beexposed to the pressure conditions in passage 29. The tube 7() extendsthrough wall 16 and cover frame 14 (FIG. l) where the other end of thetube is exposed to the atmosphere. As seen in FIG. 2, the end of tube 70in passage 29 is on the pressure gradient line E which is equal to Oinch of water above atmospheric pressure when the pressures of thefurnace and the injected air are of the desired designed values. The endof tube 70 in passage 29 is subjected to a resultant pressure of 0 inchof water above atmospheric pressure and the other end is subjected toatmospheric pressure whereby no flow occurs through tube 70. In theevent the furnace pressure exceeds the designed value, or the flow ofinjected air should cease, the inside end of tube 70 would be exposed toa positive pressure above atmospheric and warmed fluid will commence toflow out through the tube. On the other hand, if the furnace pressuredecreased below the designed value, the inside end of the tube will beexposed to a partial vacuum whereby air outside the furnace will bedrawn into the tube. Thus, if an operator wishes to determine whether itis safe to open cover 42, he places his hand adjacent the outside end ofthe tube and if no flow exists therethrough he may open the cover.Conversely, if the operator feels a warm flow of fluid issuing from thetube, he then knows it is unsafe to open the cover before appropriatesteps may be taken to correct the unsafe conditions. If the operatorfeels air being drawn into the tube, he will realize that it is safe toopen the cover.

In FIG. 4, a visual indicator, as for example a manometer 72 is employedin conjunction with tube 7i). The outside end of tube 70 is connected toone leg 74 of the manometer, while the other leg 76 is subjected toatmospheric pressure. Thus, if it is assumed that the inside end of tube70 is on the pressure gradient line E, or exposed to O inch of waterabove atmospheric pressure, in the normal operation of the furnace, thelevel of the liquid in legs 74 and 76 would be at the same height. Onthe other hand, if the furnace pressure should increase, or the ow ofinjected air is interrupted, the level of the liquid in leg 76 will behigher than the liquid level in leg 74, thereby indicating an unsafecondition for opening cover 42.

FIGS. 5 and 6 diagrammatically illustrate a modification of the presentinvention insofar as the tube 70, may if desired, be employed to governtheV operation of automatic control means which restrainsor permits`openingv of cover 42 under certain conditions. In FIG. 5, the controlmeans is shown as including a pressure capsule'or device `80 which isprovided with a flexible diaphragm 82.

One side of diaphragm '82 is subjected'to the pressure in' 90 to thewinding 92 of a solenoid 94 having an armature 96 biased outwardly ofthe solenoid by a spring 98.' Armature 96 extends through an opening ina bracket 100 and is adapted for entryl in an opening 102 in yoke 64(FIG. 6) when the latter is in the closed or'fully line position.

Considering now the operation of the structure disclosed in FIGS. 5 and6, diaphragm 82'is calibrated and designed to assume an unflexedposition under normal operation of the furnace'which results in pressureconditions in the access passage adjacent the end of tube 70 being at Oinch of water above atmospheric pressure. Under this condition, the endof pin 84 adjacent switch 88 is just touching or out of engagement withswitch member 86 whereby the switch contacts (not shown) in switch y88are closed so that solenoid 94 is energized. It will be apparentthatupon energization of the solenoid, the end of armature 96 in yoke 64movesaway from the latter and'out of openingfILOZ, whereby' member 67may be rotated to permit movement of yoke 64'to a broken line positionas seen in FIG. 2. Thus, an operator may open-cover 42. Also, if thepressure in tube 70 is below atmospheric the solenoid will be energizedto permit opening of cover 42 because diaphragm 82 flexes to the left asseen in FIG. 5, thereby moving the free end of pin 84 away from switchmember 86. Conversely, when the furnace pressure exceeds the designedvalue so as to present an unsafe condition for operation of cover 42,the pressure within tube 70'is'above atmospheric pressure and,consequently, diaphragm 82 flexes to the right. Pin 84 engages and movesswitch member 86 in a direction to disengage or break the switchcontacts (not shown) in switch 88, whereby the winding 92 of solenoid 94is deenergized. As a result, spring 98 maintains the external end ofarmature 96 in opening 102 of yoke 62 so that the latter cannot bepivoted to permit opening of cover 42.

It will now be apparent that the present invention provides a novelsafety arrangement for closure means of pressurized furnaces. Byemploying means for detecting the pressure conditions within the accesspassage, an effective safety device is provided for indicating visually,and otherwise, the unsafe and safe conditions for operating the closuremeans. In addition, the present invention, by using the indicatedpressure, may be effectively employed to prevent operation of theclosure assembly by an operator when an unsafe condition exists withinthe access passage.

Although but one embodiment ofthe invention has been illustrated anddescribed in detail, it is to be expressly understood that the inventionis not limited thereto. Various changes can be made in the arrangementof par-ts without departing from the spirit and scope of the inventionas the same will now be understood by those skilled in the art.

What is claimed is:

1. In a pressurized furnace having a furnace wall and an access passagein said wall, a safety arrangement including a cover for said passageand means for injecting fluid into said passage under a predeterminedpressure and ow to prevent the flow of combustion gases through saidpassage to the outside of the furnace when said cover is opened, saidfluid being injected so as to produce a pressure gradient in saidpassage from a negative pres-sure adjacent said cover to a positivepressure in said furnace, the combination with said cover of a safetydevice comprising a tubular member connected at one4 end tothe accesspassage to expose said one'end to'a resultant pres# sure which is equalto? or less than atmospheric pressure,

said tubular member extending outside said'furnaceancl having its otherend exposed to atmospheric pressure, and means at said other end to'sho-w the relationship between said resultantpressure and atmosphericpressure, the showing of a pressure at'said'oth'er end 'greater thanatmospheric indicating an unsafeV condition forV openingY said passage.

2. In a pressurized furnace having a furnace wall and an access passagein said wall, a safety arrangement in# cluding a cover for saidpassageand means for injecting fluid into said passage under a predeterminedpressure a pressure gradient in said passage from a negative pres'- sureadjacent said cover to a positive pressure in said furnace, thecombination with said cover of a safety device comprising a tubularmember connected at one end to the access passage to expose said one endto a resultant pressure which is equal to or'less than atmosphericpressure, said tubular member extending outside said furnace, and amanometer connected to the other end of the tubular member extendingoutside the furnace, the detection of a pressure greater thanatmospheric indicating an unsafe condition for opening said passagecover.

3. In a pressurized furnace having a furnace wall and an access passagein said wall, a safety arrangement having a cover assembly for saidaccesspassage comprisingy a cover movable relative to said wall and saidaccess passage for permitting entry to said passage in an openedposition of the cover and for sealing said passage in a closed positionof the cover, fluid directing means for injecting fluid into said accesspassage to prevent flow ofU combustion gases therethrough and outsidethe furnacefrom a negative pressure adjacentsaid cover to a positivelpressure within said furnace, pressure transmitting means connected tothe access passage and subjected to the pressure conditions therein forexposure to a resultant pressure which is equal to or less thanatmospheric pressure, latching means operable for locking the cover inthe closed position and for unlocking said cover to permit movementthereof to the opening position, and actuating means operably connectedto the latching means for rendering the latter effective or ineffectivefor locking said cover, said actuating means being connected to thepressure transmitting means and operable in response to a departure ofthe resultant pressure in the access pas` sage from a predeterminedvalue to render the latching means ineffective to unlock the cover.

4. The safety arrangement of claim 3 wherein the pressure transmittingmeans comprising a tubular member having one end at the access passageand the other end extending outside the furnace wall, said other end ofthe tubular member being connected to the actuating means to transmitthereto variations in the resultant pressure values in the accesspassage.

5. The safety arrangement of claim 4 wherein the actuating meanscomprises a pressure actuated device and a solenoid having a plungerengageable with and disengageable from the latching means to render thelatter ineffective and effective, respectively, for opening the cover,said pressure actuated device being connected to receive the resultantpressure in the access passage and further connected for actuating thesolenoid to disengage the plunger from the latching means upon departureof the resultant pressure in the access passage from a predeterminedvalue.

6. In a pressurized furnace, the combination with a furnace wall andaccess passage in the wall, a safety arrangement comprising a cover forsaid access passage, means for injecting fluid into said passage under apredetermined pressure and ow to prevent the ow of cornbustion gasesthrough the passage to the outside of the furnace when the cover isopened, said fluid being injected so as to produce a pressure gradientin said passage from a negative pressure adjacent `said cover to apositive pressure in said furnace, and pressure transmitting meansleading into said access passage positioned so as to detect under normaloperating conditions a resultant pressure in the passage which is equalto or less than atmospheric, the detection of a pressure greater thanatmospheric indicating an unsafe condition for opening said passagecover.

7. In a pressurized furnace, the combination with a furnace wall andaccess passage in the Wall, a safety arrangement comprising a cover forsaid access passage, means for injecting fluid into said passage under apredetermined pressure and ow to prevent the ow of combustion gasesthrough the passage to the outside of the furnace when the cover isopened, said fluid being injected so as to produce a pressure gradientin said passage from a negative pressure adjacent said cover to apositive pressure in said furnace, and pressure transmitting meansleading into said access passage positioned so as to detect under normaloperating conditions a resultant pressure in the passage which is equalto or less than atmospheric, said means extending through the wall ofthe furnace to the exterior thereof to render said detected resultantpressure available for use outside the furnace, the detection of apressure greater than atmospheric indicating an unsafe condition foropening said passage cover.

8. In a pressurized furnace, the combination with a furnace wall andaccess passage in the Wall, a safety arrangement comprising a cover forsaid access passage, means for injecting fluid into `said passage undera predetermined pressure and flow to prevent the ow of combustion gasesthrough the passage to the outside of the furnace when the cover isopened, said uid being injected so as to produce a pressure gradient insaid passage from a negative pressure adjacent said cover to a positivepressure in said furnace, and pressure transmitting means leading intosaid access passage positioned so as to detect under normal operatingconditions a resultant pressure Which is less than atmospheric pressure,said means extending through the wall of the furnace to the exteriorthereof and being subjected to atmospheric pressure to provide adifferential pressure which is the difference between the resultantpressure within the access passage and atmospheric pressure, thetransmission of a pressure other than said differential pressureindicating an unsafe condition for opening said passage cover.

9. In a pressurized furnace, the combination with a furnace Wall andaccess passage in the Wall, a safety arrangement comprising a cover forsaid access passage, means for injecting uid into said passage under apredetermined pressure and flow to prevent the flow of combustion gasesthrough the passage to the outside of tbe furnace when the cover isopened, said fluid being injected so as to produce a pressure gradientin said passage from a negative pressure adjacent said cover to apositive pressure in said furnace, and pressure transmitting meansincluding a tubular member leading into said access passage one end ofsaid tubular member being positioned so as to detect under normaloperating conditions a resultant pressure in said passage which is equalto or less than atmospheric, the detection of a pressure greater thanatmospheric indicating an unsafe condition for opening said passagecover.

References Cited in the file of this patent UNITED STATES PATENTS1,184,730 Ellison May 30, 1916 2,205,712 Bitgood June 25, 1940 2,362,446Bodine Nov. 14, 1944 2,512,776 Queen June 27, 1950 2,567,171 AndersonSept. 11, 1951 2,656,799 Hatton Oct. 27, 1953 2,775,216 Alexeff et alDec. 25, 1956 2,823,629 Wittke Feb. 18, 1958 FOREIGN PATENTS 223,180Australia Jan. 8, 1959 1,209,394 France Sept. 21, 1959

1. IN A PRESSURIZED FURNACE HAVING A FURNACE WALL AND AN ACCESS PASSAGEIN SAID WALL, A SAFETY ARRANGEMENT INCLUDING A COVER FOR SAID PASSAGEAND MEANS FOR INJECTING FLUID INTO SAID PASSAGE UNDER A PREDETERMINEDPRESSURE AND FLOW TO PREVENT THE FLOW OF COMBUSTION GASES THROUGH SAIDPASSAGE TO THE OUTSIDE OF THE FURNACE WHEN SAID COVER IS OPENED, SAIDFLUID BEING INJECTED SO AS TO PRODUCE A PRESSURE GRADIENT IN SAIDPASSAGE FROM A NEGATIVE PRESSURE ADJACENT SAID COVER TO A POSITIVEPRESSURE IN SAID FURNACE, THE COMBINATION WITH SAID COVER OF A SAFETYDEVICE COMPRISING A TUBULAR MEMBER CONNECTED AT ONE END TO THE ACCESSPASSAGE TO EXPOSE SAID ONE END TO A RESULTANT PRESSURE WHICH IS EQUAL TOOR LESS THAN ATMOSPHERIC PRESSURE, SAID TUBULAR MEMBER EXTENDING OUTSIDESAID FURNACE AND HAVING ITS OTHER END EXPOSED TO ATMOSPHERIC PRESSURE,AND MEANS AT SAID OTHER END TO SHOW THE RELATIONSHIP BETWEEN SAIDRESULTANT PRESSURE AND ATMOSPHERIC PRESSURE, THE SHOWING OF A PRESSUREAT SAID OTHER END GREATER THAN ATMOSPHERIC INDICATING AN UNSAFECONDITION FOR OPENING SAID PASSAGE.